1. Technical Field
Photoresist polymers and photoresist compositions containing the same are disclosed that can avoid a phenomenon where a pattern of a storage electrode contact region that receives a relatively large amount of light becomes too thin when a device isolation film pattern is formed. The photoresist polymers and compositions can also prevent pattern collapse caused by a high aspect ratio by improving the etching resistance.
2. Description of the Related Art
As a manufacturing process of a semiconductor device becomes more complicated and the degree of integration is increased, methods for forming fine patterns are needed. Because it is difficult to obtain a fine pattern with conventional photolithography using KrF (248 nm), photolithography using a far-infrared light source such as ArF (193 nm) has been developed. However, photoresist materials that have been used in ArF photolithography are more difficult to use than conventional photoresist materials. Specifically, as the critical dimension CD has been decreased by high integration, the aspect ratio of a pattern is increased which causes collapse of the photoresist pattern 12 on the semiconductor substrate 11 as shown in FIG. 1.
Semiconductor device manufacturing processes include over 100 steps. One basic step is the formation of the device isolation film. When the device isolation film pattern is formed, the same amount of light energy is irradiated on the entire field. However, a storage electrode contact region receives a relatively large amount of light due to the shape the device isolation film pattern around the electrode contact. As a result, the photoresist film is reduced in this area and the storage electrode contact region becomes thinner. Although the amount of energy or exposure conditions of lens have been regulated in order to prevent the storage electrode contact region from being too thin, the above-described problems have not been solved.
In addition, there are problems in that the margins of DOF (Depth of Focus) and EL (Energy Latitude) become smaller as the pattern becomes smaller. However, these problems cannot be solved by changing the exposure conditions. Also, it is difficult to secure etching resistance because the thickness of the photoresist film becomes too thin to prevent pattern collapse.